As the justices of the U.S. Supreme Court sit down today and review the ten petitions for certiorari involving same-sex marriage before them, Supreme Court scholar and founder of Scotusblog , Tom Goldstein , has this wonderful piece  explaining just how momentous their decision to take one or more of the cases – and how they later rule – will be.
. . . . The arc of history tilts towards equality and justice, and our society is rapidly but unevenly coming to the judgment that same-sex marriage is just and right. The claims presented by this case would just as inevitably prevail (probably by a wide margin) in the Supreme Court twenty years from now. By then, it will be broadly (if not uniformly) accepted that discrimination against homosexuals related to marriage is invidious and irrational. Our attitudes are shifting that fast.
Our country and societies around the world will read the Justices’ decision(s) not principally as a legal document but instead as a statement by a wise body about whether same-sex marriages are morally right or wrong. The issues are that profound and fraught; they in a sense seem to transcend “law.” Given the inevitably of same-sex marriage, if the Court rules against those claiming a right to have such unions recognized, it will later be judged to be “on the wrong side of history.”